KennyWRX

Hmmm, nope you are way off. Alternator output is proportional to engine rpm regardless of whether the vehicle is moving or at rest. At idle, the alternator is still providing current, however, it does charge slower. Whether the battery is charging or discharging depends on other electrical loads on the car and whether the sum of those loads exceeds what the alternator is currently providing. If the alt is putting out more that the loads, it is charging the battery, otherwise, the battery is discharging.